Features Agronomy Seeding/Planting
Manure energizes readers

September 8, 2008

Last month I wrote about the potential – and multiple benefits – of turning livestock manure and agricultural waste into methane, using a process called anaerobic digestion. That methane is then used to generate electricity.

Readers responded with the same question I had: Why isn't the province doing a better job of getting these rural clean-energy systems connected to the grid?

It got me realizing that this technology isn't limited to the farm, either. There are a number of ways that anaerobic digester systems, or ADs, can be put to use in urban and suburban settings.

This is something Toronto-based Yield Energy is working on. The company has plans to build a 3.2 megawatt AD system near Pearson airport, using a variety of commercial and industrial organic waste collected around the area – roughly 60,000 tonnes of waste every year. Yield has the backing of the Toronto and Region Conservation Authority, which wants to promote the use of such systems in urban environments.

"The airport is one of several projects we're working on at this time," says John Thomson, the company's chief executive officer. He says the facility will likely start producing electricity in the summer of 2009.

The project involves Peel Region, the Greater Toronto Airports Authority, and a number of industrial and commercial operations clustered in the area.

All partners will supply food waste and other organic materials that would otherwise go to landfill. This includes leftover food from airplanes.

Another three-megawatt project, this one in an industrial area of Scarborough, will use organic waste from grocery stores, restaurants and other businesses.
The waste is generated locally, processed locally, and will end up contributing electricity locally. Waste heat from the process will also be used by nearby companies to preheat water going into their industrial boilers.

"To me the concept of throwing our organic waste into the back of a truck and hauling it hundreds of kilometres to another location makes absolutely zero sense," says Thomson.

"If you can literally treat your materials where they're generated, then it's a brilliant model."

Toronto has its Green Bin initiative and the organic material collected from this program is treated in a similar way.

For the most part, it has worked quite well for residential organic waste. Unfortunately, the biogas that's produced from the main Dufferin anaerobic digester is not yet used to generate electricity for the grid – a wasted opportunity. Power won't be generated until two new digesters have been built – another at Dufferin and a new one at the Disco Transfer Station in Etobicoke.

And the Green Bin program currently doesn't include multi-unit dwellings, such as apartments and condominiums, which house about half of Toronto's residents. The city did launch a pilot program that it intends to expand to all multi-unit dwellings, but a lack of processing capacity has stalled the effort.

Meanwhile, commercial and industrial organizations across the city continue to operate outside of the Green Bin program, representing a huge amount of organic waste that often ends up in landfill.

Yield Energy is aiming for the commercial and industrial side of the market, but it also sees potential with multi-unit dwellings. Thomson says he can see a time when clusters of apartments or condominiums have their own anaerobic digester system right on site, meaning no expensive and energy-intensive hauling and an ability on site to produce electricity and heat for surrounding buildings.

Having dozens of these systems spread across the GTA could bring added stability to the city's electricity system while addressing a tricky waste-management problem. Waste heat from the systems could also be used to preheat hot water in the nearby buildings, creating a mini-district heating system.

It's technically possible today, but in Thomson's mind the economics don't fit.

The only way to make money processing organic residential waste in Ontario is to achieve economies of scale.

But down the road, as energy prices increase and greenhouse-gas trading markets emerge, the story might change. Smaller anaerobic digesters might begin to make economic sense, particularly if the operators of these systems get to keep their carbon credits, Thomson says.

(Carbon credits can be earned because when burning biogas to generate electricity, it turns methane into carbon dioxide, reducing the potency of the greenhouse gas by a factor of 21.)

"It will be a natural next step," he says. "It's just going to take time for North Americans to wrap their heads around it. We just don't have that mindset today.

"It's fascinating to me that here it is so new for us, yet in Germany you turn a corner and there's another biogas plant, maybe sitting beside a tennis court or at the back of a cafeteria."